This invention relates to an oil seal ring of a synthetic resin mainly for use in sealing hydraulic oil in an automatic transmission such as a torque converter or a hydraulic clutch.
Some conventional seal rings of this type are formed from cast iron and others from PTFE (tetrafluoroethylene resin). Some of more recent seal rings are formed by injection-molding a synthetic resin to improve wear resistance and oil sealing properties and to reduce production cost.
Such a seal ring is fitted between a rotary shaft and a cylinder so as to rotate when both members rotate relative to each other and to slide when they move axially relative to each other. It is required to be capable of maintaining sufficient sealing properties even if the rotary shaft and the cylinder runs out or vibrate.
One problem with an oil seal ring formed by injection molding a synthetic resin, especially a large size ring in diameter and circumference, is that if the position of the material injection gate is improper, its dimensions and the composition of material tend to be uneven.
An object of the present invention is to provide an oil seal ring of a synthetic resin having uniform properties over the entire length of the ring by setting the injection point at such a position that dimensions of the ring and its material composition will be uniform.
Another object of the invention is to provide a mold for injection molding the abovementioned oil seal ring of a synthetic resin.